diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..ebfc1ed
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "sepatch"
+version = "0.1.0"
diff --git a/src/main.rs b/src/main.rs
index 4e25371..e6a8ffe 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,4 @@
-use std::{fs, io::{self, BufRead, BufReader, Write}, fmt::format};
+use std::{fs, io::{self, BufRead, BufReader, Write}};
 
 fn main() {
     let args : Vec<String> = std::env::args().collect();
@@ -13,6 +13,10 @@ fn main() {
             return;
         }
     };
+    if let Err(e) = verify_code(&codes) {
+        println!("verify code error: {}", e.to_string());
+        return;
+    }
     if let Err(e) = apply_code(args[1].as_str(), &codes) {
         println!("apply code error: {}", e.to_string());
     }
@@ -22,7 +26,7 @@ fn read_codes(code_file : &str) -> io::Result<Vec<(u32, u32)>> {
     let file = fs::File::open(code_file).expect("cannot open patch_code");
     let reader = BufReader::new(file);
     let mut codes = Vec::new();
-    let mut lines = 0u32;
+    let mut lines = 1u32;
     for line in reader.lines() {
         if let Ok(l) = line {
             let r_str = l.as_str();
@@ -35,31 +39,218 @@ fn read_codes(code_file : &str) -> io::Result<Vec<(u32, u32)>> {
                     codes.push((lines, val2.unwrap()));
                 }
             } // else skip
+            lines += 1;
         }
     }
     Ok(codes)
 }
 
-fn verify_code(codes : Vec<(u32, u32)>) -> Result<(), String> {
-    let pos = 0usize;
-    while pos < codes.len() {
+fn verify_code(codes : &Vec<(u32, u32)>) -> Result<(), String> {
+    let mut pos = 0usize;
+    let max_len = codes.len();
+    let mut search_code = false;
+    while pos < max_len {
+        let line = codes[pos].0;
         let first_code = codes[pos].1;
-        let op_code = first_code >> 28;
-        let mut search_code = false;
+        let op_code = (first_code >> 28) as u8;
         match op_code {
             0x0 | 0x1 |0x2 => {
-                return Err(format!("{}", 123));
+                if search_code {
+                    if first_code & 0xf000000 != 0x8000000 {
+                        return Err(format!("wrong code at line {}: need search code after search", line));
+                    }
+                    search_code = false
+                }
+                if pos + 2 > max_len {
+                    return Err(format!("wrong code at line {}: unexpected end", line));
+                }
+                pos += 2;
+            }
+            0x4 => {
+                if search_code {
+                    if first_code & 0xf000000 != 0x8000000 {
+                        return Err(format!("wrong code at line {}: need search code after search", line));
+                    }
+                    search_code = false
+                }
+                if pos + 4 > max_len {
+                    return Err(format!("wrong code at line {}: unexpected end", line));
+                }
+                pos += 4;
+            }
+            0x5 => {
+                if search_code {
+                    return Err(format!("wrong code at line {}: need search code after search", line));
+                }
+                if pos + 4 > max_len {
+                    return Err(format!("wrong code at line {}: unexpected end", line));
+                }
+                pos += 4;
+            }
+            0x8 => {
+                if search_code {
+                    return Err(format!("wrong code at line {}: need search code after search", line));
+                }
+                let search_bytes = (first_code & 0xffff) as usize;
+                if search_bytes == 0 {
+                    return Err(format!("wrong code at line {}: search length should not be 0", line));
+                }
+                let code_len = ((search_bytes - 1) / 4 + 1) * 2;
+                if pos + code_len > max_len {
+                    return Err(format!("wrong code at line {}: unexpected end", line));
+                }
+                search_code = true;
+                pos += code_len;
+            }
+            0xa => {
+                if search_code {
+                    return Err(format!("wrong code at line {}: need search code after search", line));
+                }
+                if pos + 1 >= max_len {
+                    return Err(format!("wrong code at line {}: unexpected end", line));
+                }
+                let write_bytes = codes[pos + 1].1 as usize;
+                if write_bytes == 0 {
+                    return Err(format!("wrong code at line {}: write length should not be 0", line));
+                }
+                if write_bytes > 320 {
+                    return Err(format!("wrong code at line {}: write length should not exceed 320", line));
+                }
+                let code_len = ((write_bytes - 1) / 8 + 1) * 2 + 2;
+                if pos + code_len > max_len {
+                    return Err(format!("wrong code at line {}: unexpected end", line));
+                }
+                pos += code_len;
+            }
+            _ => {
+                return Err(format!("unknown code at line {}", line));
             }
-            _ => (),
         }
-        pos += 1;
+        
     }
     Ok(())
 }
 
-fn apply_code(patch_file : &str, codes : &Vec<(u32, u32)>) -> io::Result<()> {
-    let data = fs::read(patch_file)?;
-    let mut write_file = fs::OpenOptions::new().write(true).truncate(true).open(patch_file)?;
-    write_file.write(data.as_slice())?;
+fn apply_code(patch_file : &str, codes : &Vec<(u32, u32)>) -> Result<(), String> {
+    let fn_map_err = |e : io::Error| format!("apply code error: {}", e.to_string());
+    let mut data = fs::read(patch_file).map_err(fn_map_err)?;
+    let mut pos = 0usize;
+    let max_code_len = codes.len();
+    let max_data_len = data.len();
+    let mut search_addr : Option<u32> = None;
+    while pos < max_code_len {
+        let line = codes[pos].0;
+        let first_code = codes[pos].1;
+        let op_code = (first_code >> 28) as u8;
+        match op_code {
+            0x0 => {
+                let val = codes[pos + 1].1 as u8;
+                let addr = if let Some(saddr) = search_addr {
+                    search_addr = None;
+                    (codes[pos].1 & 0xffffff) + saddr
+                } else {
+                    codes[pos].1 & 0xfffffff
+                } as usize;
+                if addr >= max_data_len {
+                    return Err(format!("apply code error at line {}: address overflow", line));
+                }
+                data[addr] = val;
+                pos += 2;
+            }
+            0x1 => {
+                let val = codes[pos + 1].1 as u16;
+                let addr = if let Some(saddr) = search_addr {
+                    search_addr = None;
+                    (codes[pos].1 & 0xffffff) + saddr
+                } else {
+                    codes[pos].1 & 0xfffffff
+                } as usize;
+                if addr + 1 >= max_data_len {
+                    return Err(format!("apply code error at line {}: address overflow", line));
+                }
+                data[addr] = (val & 0xff) as u8;
+                data[addr + 1] = ((val >> 8) & 0xff) as u8;
+                pos += 2;
+            }
+            0x2 => {
+                let val = codes[pos + 1].1;
+                let addr = if let Some(saddr) = search_addr {
+                    search_addr = None;
+                    (codes[pos].1 & 0xffffff) + saddr
+                } else {
+                    codes[pos].1 & 0xfffffff
+                } as usize;
+                if addr + 3 >= max_data_len {
+                    return Err(format!("apply code error at line {}: address overflow", line));
+                }
+                data[addr] = (val & 0xff) as u8;
+                data[addr + 1] = ((val >> 8) & 0xff) as u8;
+                data[addr + 2] = ((val >> 16) & 0xff) as u8;
+                data[addr + 3] = ((val >> 24) & 0xff) as u8;
+                pos += 2;
+            }
+            0x4 => {
+                let mut val = codes[pos + 1].1;
+                let mut addr = if let Some(saddr) = search_addr {
+                    search_addr = None;
+                    (codes[pos].1 & 0xffffff) + saddr
+                } else {
+                    codes[pos].1 & 0xfffffff
+                } as usize;
+                let mut count = (codes[pos + 2].1 & 0xfff0000) >> 16;
+                let addr_diff = codes[pos + 2].1 & 0xffff;
+                let val_diff = codes[pos + 3].1;
+                while count != 0 {
+                    if codes[pos].1 & 0xf000000 == 0x1000000 {
+                        if addr >= max_data_len {
+                            return Err(format!("apply code error at line {}: address overflow", line));
+                        }
+                        data[addr] = (val & 0xff) as u8;
+                    } else if codes[pos].1 & 0xf000000 == 0x2000000 {
+                        if addr + 1 >= max_data_len {
+                            return Err(format!("apply code error at line {}: address overflow", line));
+                        }
+                        data[addr] = (val & 0xff) as u8;
+                        data[addr + 1] = ((val >> 8) & 0xff) as u8;
+                    } else {
+                        if addr + 3 >= max_data_len {
+                            return Err(format!("apply code error at line {}: address overflow", line));
+                        }
+                        data[addr] = (val & 0xff) as u8;
+                        data[addr + 1] = ((val >> 8) & 0xff) as u8;
+                        data[addr + 2] = ((val >> 16) & 0xff) as u8;
+                        data[addr + 3] = ((val >> 24) & 0xff) as u8;
+                    }
+                    count -= 1;
+                    addr += addr_diff as usize;
+                    val += val_diff;
+                }
+                pos += 4;
+            }
+            0x5 | 0x8 => {
+                return Err(format!("apply code error at line {}: not supported", line));
+            }
+            0xa => {
+                let mut addr = (codes[pos].1 & 0xfffffff) as usize;
+                let write_bytes = codes[pos + 1].1 as usize;
+                if addr + write_bytes>= max_data_len {
+                    return Err(format!("apply code error at line {}: address overflow", line));
+                }
+                let mut bytes = 0;
+                while bytes < write_bytes {
+                    let offset = pos + 2 + (bytes / 4);
+                    let shift = (3 - (bytes % 4)) * 8;
+                    data[addr] = ((codes[offset].1 >> shift) & 0xff) as u8;
+                    bytes += 1;
+                    addr += 1;
+                }
+                let code_len = ((write_bytes - 1) / 8 + 1) * 2 + 2;
+                pos += code_len;
+            }
+            _ => ()
+        }
+    }
+    let mut write_file = fs::OpenOptions::new().write(true).truncate(true).open(patch_file).map_err(fn_map_err)?;
+    write_file.write(data.as_slice()).map_err(fn_map_err)?;
     Ok(())
 }